Selecting Your Subject
The first thing to consider when deciding upon the person to write about is whether you are truly interested in him. Sometimes, you'll settle on someone with whom you share common interests, which can provide the added benefit of establishing your qualifications to write the biography. Let us suppose you have always been a biking enthusiast and have even competed in races and now would like to write a biography of Lance Armstrong. Your interest and experience in biking helps make you suitable to write the biography.
There is another more important reason you must be attracted to the subject of your book: since it's likely you will be immersing yourself in the life of your subject for two years or more, you had better find her interesting!
If the subject of a biography designates you to write the biography, the book can be promoted as “an authorized biography,” which provides access to much information and encourages people to agree to be interviewed. Without an endorsement, it is improper to employ this term, although sometimes, for marketing and sensationalist purposes, the phrase “unauthorized biography” is touted.
Another consideration in choosing whom you write about concerns the issue of cooperation. If the subject is alive, having his cooperation would be beneficial not only in interviewing the subject but in gaining access to information and the ability to interview others. Should the subject be deceased, securing the assistance and support of the estate or heirs can prove invaluable for similar reasons.